The development of magnetic resonance imaging (MRI) contrast agents is important to human health given the increasing importance of MRI diagnostics. An important new development in this area is based on the discovery of Ln(lll) complexes that function as MRI contrast agents by chemical exchange saturation transfer (CEST) processes. Unlike the more conventional Gd(lll) contrast agents, Ln(lll) CEST agents may contain almost any of the paramagnetic Ln(lll). In order to develop more effective contrast agents, it is important to study Ln(lll) coordination chemistry including water ligand exchange rates, coordination number and variations across the Ln(lll) series. [unreadable] [unreadable] The goal of the proposed research is to use direct-excitation (non-ligand sensitized) luminescence spectroscopy of Nd(lll), Sm(lll), Eu(lll), Dy(lll) and Yb(lll) to study the coordination chemistry of Ln(lll) contrast agents. A new laser system set up at the University of Buffalo, will be used for this work. There are three major research objectives including: 1) to determine the conditions for the direct-excitation luminescence of Nd(lll), Sm(lll), Eu(lll), Dy(lll) and Yb(lll) complexes and quantitate selected ligand group excited state quenching constants, 2) to utilize the short luminescence lifetimes of Sm(lll), Dy(lll) and Yb(lll) to study a dynamic equilibrium between eight and nine coordinate Ln(lll) complexes and to obtain rate constants for ligand exchange for Eu(lll) complexes, 3) to evaluate the potential of mononuclear Ln(lll) macrocyclic complexes containing pendent alcohol groups and dinuclear Ln(lll) complexes as MRI contrast agents. This work will contribute to a better basic understanding of Ln(lll) coordination chemistry and will yield new tools for Ln(lll) research in biological and chemical systems. The new laser system will also be available to researchers throughout the country and will be at the heart of a center for Ln(lll) luminescence research. [unreadable] [unreadable] [unreadable]